Tomcat GC日志语句的说明 [英] Explanation of Tomcat GC log statements

问题描述

下面是我的catalina.out中的一条声明，由我的tomcat服务器生成：

1885.855：[GC [PSYoungGen：742996K-> 64359K（761472K）] 2509583K - > 1832973K（4116928K），0.1453610秒] [Times：user = 0.31 sys = 0.00，real = 0.14 secs]

有人可以在这里解释各种数字的含义？

解决方案

该行的分解如下：

<这个以秒为单位的时间是JVM运行的时间，所以在你的情况下大约31分钟左右，GC发生在这个时间点。 p>

[GC - 表示此时发生GC。这是一个部分GC，有时它会显示 Full GC

现在，可用于JVM的总堆= Young + Old

[PSYoungGen：742996K-> 64359K（761472K） - 表示并联清理收集器年轻一代（这是JVM中可用的许多类型的GC收集器之一）。

GC释放的内存始终是模式

  x - > y（z）
  

x是GC之前的初始记忆，y是
GC之后的内存，z是在
JVM中允许用于该区域的总
内存

因此在您的示例中，
742996K-> 64359K（761472K） - 总年轻规模为761Mb，当它达到742 Mb a时收集发生，清理到64.3Mb
，即清理了678 Mb。 （4116928K）

这里表示了总堆内存。
因此，在GC的总数可能达到4.1 Gb时，当GC发生时，它已经填充了2.5 Gb，降到了1.83 Gb--同样的678 Mb也被清除了。

  0.1453610秒] 
  

整个操作耗时0.1453610秒
$ b $ pre $ [Times：user = 0.31 sys = 0.00，real = 0.14秒]


显示了

这只是一行 - 你会寻找一个模式，特别是 Full GC 其中
并使用日志分析器，如 GCViewer ，用于向您显示吞吐量和其他好东西。

另请阅读

进一步阅读：

http ：//sujitpal.blogspot.com/2006/08/charting-jvm-garbage-collection.html

垃圾收集日志消息

Here is a statement from my catalina.out, generated by my tomcat server :

1885.855: [GC [PSYoungGen: 742996K->64359K(761472K)] 2509583K->1832973K(4116928K), 0.1453610 secs] [Times: user=0.31 sys=0.00, real=0.14 secs]

Could someone explain the meaning of various numbers in here?

解决方案

The break-up of the line is as followd:

1885.85 - this in seconds is the amount of time the JVM has been running, so around 31 minutes or so in your case at which point the GC took place.

[GC - states a GC occured at this point in time. This is a Partial GC, sometimes it will show Full GC

Now, the Total Heap available for the JVM = Young + Old

[PSYoungGen:742996K->64359K(761472K) - represents the Parallel Scavenging Collector in the Young generation (which is one of the many types of GC collectors available in the JVM).

The memory freed by GC is always of the pattern

x->y(z) 

x is the initial memory before GC, y is the memory after GC, z is the total memory allowed for that area in the JVM

so in your example, 742996K->64359K(761472K) - the total Young size is 761Mb, and when it reached 742 Mb a collection took place, and it cleared down to 64.3Mb i.e. it cleared up 678 Mb

2509583K->1832973K(4116928K)

Here the total heap memory is represented. So out of a total possible heap of 4.1 Gb, when the GC took place, it had filled 2.5 Gb and it has come down to 1.83 Gb - again the same 678 Mb is what got cleared.

0.1453610 secs]

This entire operation took 0.1453610 seconds

[Times: user=0.31 sys=0.00, real=0.14 secs] 

shows the break-up of user, system and real times taken.

This is just one line - you would be looking for a pattern esp one that says Full GC in it And use a log analyzer like GCViewer for showing you throughput and other good stuff.

Also read the docs from Sun to get the basics.

Further reading:

http://sujitpal.blogspot.com/2006/08/charting-jvm-garbage-collection.html

Java Garbage Collection Log messages

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